Efficacy and safety of PLDR‐IMRT for the re‐irradiation of recurrent NPC: A prospective, single‐arm, multicenter trial

Salvage treatment of locoregionally recurrent nasopharyngeal carcinoma (NPC) requires weighing the benefits of re‐irradiation against increased risks of toxicity. Here, we evaluated the outcomes of patients treated with intensity‐modulated‐based pulsed low‐dose‐rate radiotherapy (PLDR‐IMRT) to enhance the curative effect of salvage treatment and reduce RT‐related SAEs. A prospective clinical trial was conducted from March 2018 to March 2020 at multiple institutions. NPC patients who experienced relapse after radical therapy were re‐irradiated with a median dose of 60 Gy (50.4–70 Gy)/30 f (28–35 f) using PLDR‐IMRT. Thirty‐six NPC patients who underwent PLDR‐IMRT for locoregional recurrence were identified. With a median follow‐up of 26.2 months, the objective response rate (ORR) of the entire cohort was 91.6%. The estimated mPFS duration was 28 months (95% CI: 24.9–31.1), and the estimated mLRFS duration was 30.4 months (95% CI: 25.2–35.5). The overall survival (OS) rate for all patients was 80.6%, the progression‐free survival (PFS) rate was 75% and the cancer‐specific survival (CSS) rate was 88.9% at 1 year. The LRFS and DMFS rates were 88.9% and 91.7%, respectively, at 1 year. A combination of systematic therapies could provide survival benefits to patients who experience NPC relapse (p < 0.05), and a Karnofsky performance status (KPS) score of ≥90 was a favorable factor for local control (p < 0.05). The incidence of acute SAEs (grade 3+) from PLDR was 22.2%, and the incidence of chronic SAEs was 19.4% among all patients. PLDR‐IMRT combined with systematic therapy can effectively treat patients with locoregionally recurrent nasopharyngeal carcinoma and causes fewer adverse events than the rates expected with IMRT.